Gaussian beams are by far the most common beam used for performing laser dicing. This is mainly attributed to a fact that a Fourier transform of the Gaussian beam remains a Gaussian beam and preserves its intensity profile when passing through complex lens and optical systems. However, in many laser fabrication applications, the short Rayleigh range (length before a laser beam diverges) of the Gaussian beam often limits the penetration depth into a sample and imposes additional requirements on the sample.
Compared with Gaussian beam, Bessel beams exhibit unique properties in research and industrial applications. Bessel beam is a “non-diffracting” beam, and its transverse intensity profile does not vary as it propagates, making it the ideal laser beam to perform laser dicing. Since the Bessel beam's waist is narrower than the Gaussian beam, superior cutting results in terms of both resolution and speed can be achieved.
In addition, during a conventional stealth dicing (SD) process, a SD modified layer formed by using the Gaussian beam is relatively thin by one pass. If a thick sample is diced, a plurality of SD modified layer is needed for cutting or dicing. When a sample (e.g. a wafer or a substrate) is thick, many passes (>10) need to be scanned at different depths, the resolution of the dicing results and the dicing speed may be reduced.
Therefore, there is a need for improved systems and methods for dicing samples by a Bessel beam matrix.